Autor: Staff

~ 08/05/09

Early indications show that nutritional supplements may lessen muscle atrophy brought on by space travel, prolonged bed confinement or immobility. To study space travel’s effect on muscles, Dr. Robert Wolfe of the University of Texas Medical Branch at Galveston enlisted healthy subjects to stay in bed 28 days during a National Space Biomedical Research Institute study.

“One cause of muscle atrophy in space is lack of muscular activity. That’s why bed rest is a good model because it minimizes activity, and like astronauts, you lose muscle mass primarily in the legs,” said co-investigator Dr. Arny Ferrando, a professor of surgery at UTMB and Shriners Hospital for Children in Galveston. “When muscles are inactive, as they are in space, they don’t make new proteins. If muscle breakdown rates are the same, that means you lose muscle.”

Researchers are attempting to increase protein synthesis rates with supplements of amino acids, which are the raw materials of protein. Participants received the supplements three times a day, and researchers compared the protein synthesis/breakdown rates and muscle mass before and after the bed-rest study. This data was compared to results from a control group that received a placebo drink instead of the supplements.

“Early results suggest that the amino acid supplement is able to maintain synthesis rates and body mass,” Ferrando said.

During the study, subjects must remain in bed and can get up only briefly to use a bedside commode. They eat and bathe from their beds, and daily activities encompass watching television, reading books and using a bedside computer.

Midway through the study, researchers determine muscle mass and function by testing the subjects’ strength and body composition.

They gather the most vital data, the protein synthesis and breakdown rates, by using stable isotope analysis. With the stable isotope technique, researchers attach a harmless tracer to specific amino acids that travel through the bloodstream. Then, they take blood samples to determine the amount of amino acids that enter and exit the leg.

“If 80 amino acids are coming into the artery and 60 are going out of the vein, we know that 20 were probably made into proteins in the muscle,” said Dr. Douglas Paddon-Jones, also of UTMB and a co-investigator performing these studies. “We complete the muscle analysis by removing a small piece of muscle and determining how many amino acids have been incorporated into proteins. Over time, we can calculate the rate at which the synthesis and breakdown occurs.”

Space conditions also elevate the body’s level of the stress hormone cortisol, which increases the breakdown rate of proteins. “Under stress, the body breaks down proteins to make energy for survival,” said Ferrando, a member of NSBRI’s nutrition and fitness research team. “However, this process also causes muscle atrophy.”

To study the supplement’s effects on muscle loss due to elevated levels of cortisol, researchers infused the stress hormone into the participants’ blood during the stable isotope tests. The researchers mimic the cortisol concentrations found during space flight, then determine protein synthesis and breakdown rates of the subjects taking the supplement and compare this to the rates of the control group.

Ferrando and Wolfe are also collaborating with other NSBRI researchers who use the subjects’ body fluids to study changes in bone, immune function and cell damage induced by bed rest.

Findings from this research on nutritional supplements could benefit patients on Earth.

“Muscle atrophy is common in many populations: the elderly, kids with burns, patients in intensive care or people who have had major operations. We’re looking at this phenomenon in terms of space flight, but the study has many other implications,” Ferrando said.

———————————–
Article adapted by MD Sports from original press release.
———————————–

Contact: Kathy Major
National Space Biomedical Research Institute 

The NSBRI’s consortium members include Baylor College of Medicine, Brookhaven National Laboratory, Harvard Medical School, The Johns Hopkins University, Massachusetts Institute of Technology, Morehouse School of Medicine, Mount Sinai School of Medicine, Rice University, Texas A&M University, University of Arkansas for Medical Sciences, University of Pennsylvania Health System and University of Washington.

Autor: Staff

~ 06/05/09

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Research News

 In many HIV-infected individuals with prior weight loss, the failure to regain weight and lean tissue is at least in part the consequence of inadequate protein intake or ingestion of a poor-quality protein rather than total caloric intake. Dietary sources of protein are presumably inadequate to meet the high metabolic needs caused by HIV infection. To achieve a target protein intake in the range (1.5 to 2.0 g/kg/day) demonstrated in other catabolic diseases necessary to achieve positive nitrogen balance and to generate substantial anabolic effects.

A high-quality protein food supplement may help HIV-positive patients maintain, and possibly gain, muscle mass. Many HIV-positive patients lose weight that they are then unable to regain. This may be because patients are not eating enough protein or are not eating the right kinds of protein. The protein eaten in foods (such as meat, eggs, or beans) may not be able to make up for the amount of protein lost due to HIV infection.

Autor: Staff

~ 05/05/09

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Research News

Nitrogen Balance

By Sandco Staff

The sensitivity of Nitrogen balance to changes in energy intake has been demonstrated in numerous studies. It is well known that when diet provides adequate amounts of protein the addition of energy-yielding nutrients (either carbohydrate or fat) results in a linear improvement in N balance in humans and animals (Munro, 1951, 1964, 1978; Inoue et al. 1973; Garza et al. 1976; Reeds et al. 1981). However, the underlying biochemical mechanism whereby energy intake above requirements affects N metabolism in long-term studies remains obscure.

 

References:

Munro, H. N. (1951). Carbohydrate and fat as factors in protein utilization and metabolism. Physiological Reviews 31, 449488.
Munro, H. N. (1964). General aspects of the regulation of protein metabolism by diet and by hormones. In Mammalian Protein Metabolism, vol. 1, pp. 381481 [H. N. Munro and J. B. Allison, editors]. New York:
Academic Press.
Munro, H. N. (1978). Energy and protein intakes as determinants of nitrogen balance. Kidney International 14, 313-316.
Inoue, G., Fujita, Y. & Niiyama, Y. (1973). Studies on protein requirements of young men fed egg protein and rice protein with excess and maintenance energy intakes. Journal of Nutrition 103, 1673-1687.
  

Garza, C., Scrimshaw, N. S. & Young, V. R. (1976). Human protein requirements: the effect of variations in energy intake within the maintenance range. American Journal of Clinical Nutrition 29, 28G287
Reeds, P. J., Fuller, M. F., Cadenhead, A,, Lobley, G. E. & McDonald, J. D. (1981). Effects of changes in the intakes of protein and non-protein energy on whole-body protein turnover in growing pigs. British Journal of Nutrition 45, 539-546.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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